This invention relates to a method of connecting an electronic element to a base plate without using any solder material.
Methods of connecting an electronic element to a base plate without using a solder material, or the so-called solderless connecting methods, include mechanical compression by using rubber or a so-called zebra rubber material as well as thermal compression by using a so-called anisotropic conductive adhesive material obtainable by mixing small metallic or carbon particles into an adhesive base. Base plates for these electronic elements may be produced by etching a copper plate and thereafter plating its surface with Au or Sn or by directly printing a wiring pattern with carbon or a conductive ink material such as Ni and Cu. Although a plate made by the latter method has a rather large margin of error in the wiring resistance and its wiring pitch is not very accurate. Somewhere between these two types of base plates are those obtainable by printing a wiring pattern with a conductive ink material on a polyester film or the like with a laminated or vapor deposited Al or Cu foil and thereafter etching and cleaning. With conventional wiring base plates of this type, however, oxide films tend to be formed, as time passes, between the conductive ink layer and the metallic wiring layer of Al or Cu therebelow. This phenomenon causes to reduce the adhesive force between the conductive ink material and the metallic wiring pattern, that is, the electric properties of the connected element deteriorate with time.